A heat pump dual temperature display cabinet using natural refrigerants

Abstract

The dual-temperature display cabinet stores hot and cold products in the same unit and requires a heat source in addition to the refrigeration system. In these systems, the condensing heat from the vapor compression system can be conveniently recovered. The remaining challenge is to find a proper environmentally friendly refrigerant that matches this application. To address this challenge, three natural fluids and a zeotropic mixture were investigated in this study, namely R290, R744, R600, and R290/R600. Experimental data from a baseline dual-temperature display cabinet validated the numerical model in this study. It was found that the most important parameter is the air flowrate of the condenser, and the underlying principle is balancing the heating and cooling energy consumption for better comprehensive system performance. We found that R744 is superior to R290 at low ambient temperatures but fails to compete with R290 at high ambient temperatures. To overcome this challenge and exploit the temperature glide of zeotropes, R290/R600 mixture was proposed and demonstrated a robust energy-saving benefit from R290. The power consumption of dual-temperature open display cabinet using R290/R600 mixture is 9.2%, 12.2%, 14.6%, and 10.9% lower than the baseline (R290), at 15 °C, 20 °C, 25 °C, and 32 °C, respectively.